How do you execture the subdivide function on the multiresolution modifier in python?
as you see in API 


  bpy.ops.object.multires_subdivide(modifier="") Add a new level of
  subdivision


you can test this:

bpy.ops.object.modifier_add(type='MULTIRES')
bpy.context.object.modifiers["Multires"].name = "A"
bpy.context.object.modifiers["A"].subdivision_type = 'CATMULL_CLARK'
bpy.ops.object.multires_subdivide(modifier="A")